| Currently, the heating system gives first place to the cola-fired and gas-fired boiler system in Hexi Corridor, which is of high energy consumption and serious pollution; therefore, an energy-saving, environmentally-friendly heating system is a priority of great concern and to be addressed. Based on the improved life cycle assessment method, this paper has, taking into overall consideration the climatic characteristics and energy structure features of Hexi Corridor, established a life cycle assessment index system of heating system for Hexi Corridor, based on which optimized algorithm is used to obtain the optimum heating system suitable for Hexi Corridor—solar energy and CO2air-source heat pump combined heating system. Experiment and simulated computation models are integrated to make detailed, in-depth study on the system. The study results may provide theoretical basis and technical reference for the design of solar and CO2air-source heat pump combined heating system in Hexi Corridor.In this paper, an experimental research is performed on the solar collector heating system and the CO2air-source heat pump heating system respectively. The results indicate that the law is that the heat collector outlet is low in temperature and has a large temperature difference caused by a large flow rate, but the mean temperature of inlet and outlet is the same under the different flow rates. Using the dynamic measurement method, the solar fraction of the used heat collector can be calculat, and the linear fit formula for instantaneous efficiency of the used heat collector is η=0.627-0.357*. The experimental results of CO2air-source heat pump indicate that water inlet temperature and flow at water side of the gas cooler as well as outdoor temperature and air flow at air side of the evaporator are primary factors to affect the system COP, and the unit COP is ranging from2to3when the CO2air-source heat pump is in a low-temperature condition of-25℃～15℃.In this paper, the mathematical model and simulated calculation model are established for the solar energy and CO2air-source heat pump combined heating system based on the infinitesimal method, and TRNSYS is applied to make coupling solutions of all models of the system. Furthermore, the simulation and experimental data is compared to verify the reliability of the simulated model.The impact of the unit performance on the gas cooler, evaporator and heat regenerator of the CO2air-source heat pump under low temperature is analyzed The impact of the unit performance on the gas cooler of the results indicate that, while under a low temperature, the heating capacity would be continuous reduced with the increase of inlet water temperature of the gas cooler. In addition, increased water inflow of the gas cooler can improve the coefficient of performance (COP) of the unit, but also can reduce the water outflow temperature, thus, water inflow shall be chosen properly according to actual demands. Judging from the impacts of the outdoor temperature and air flow at air side of the evaporator on the unit performance, the unit COP decreases with the drop of outdoor temperature; the increased air flow may improve the unit COP, yet the increasing air flow has less and less impacts on the COP. Therefore, in actual application when outdoor temperature is in a low-temperature condition, in order to make the unit COP is maintained at a higher level, may be by adjusting the air flow and other methods to achieve. The study results on heat regenerator show that the average COP of units with heat regenerators are5%higher than those without heat regenerators;This paper also makes simulation study on operating characteristics of the solar and CO2air-source heat pump combined heating system based on typical clear day, cloudy day and cloudy three conditions, and the impact of collector area on the performance of CO2air-source heat pump is analyzed. The results indicate that in three working conditions, the COP of the unit would gradually increase with the increase of collector area. Meanwhile, the COP would gradually increase with the increase of solar radiation. For instance, when the collector area is600m2, of which, the energy saving rate of the CO2air source heat pump is24.9%higher than that when the collector area Om2; the energy saving rate in a typical cloudy day is19.2%lower than that in the sunny day. Through the analysis of energy consumption, the solar equivalent generation power efficiency ηsegp and the comprehensive efficiency of collector is defineded. The collector area is optimized through the comprehensive efficiency, thus obtaining the optimal the solar fraction of this area in the heating season is27.7%. Based on the optimal the solar fraction, the relation expression between the collector area and the heating capacity of CO2air-source heat pump unit, when the combined heating system is used in actual engineering, isThe control strategy of the solar energy and CO2air-source heat pump combined heating system is established. Propose the monitoring parameters through determining the control objective of the system, comprehensively introduce the seven operation modes of the solar energy and CO2air-source heat pump combined heating system under the optimal operation conditions, introduce the converting conditions of each operation mode based on the control principle by making examples, and finally determine the control strategy as well as verify its reliability through case analysis. |
PDF Full Text Request